Hydraulic radial piston engines are used for example for driving a transmission of a concrete mixer on a truck, as disclosed in DE 10 2004 057 849 A1. In such cases a housing portion, in which a distributor is arranged, is bolted to a further housing portion, with a cam disk arranged between the two housing portions. A rotary cylinder, which in operation turns about a rotational axis, has radially positioned pistons which are in active connection with the cam disk and, in the operating condition, is supported by a bearing on the further housing portion. For servicing purposes the bolts which fix the housing portion and the rotary cylinder to the further housing portion are removed, and the hydraulic radial piston engine is dismantled from the concrete mixer truck in individual components. The complete assembly cannot be exchanged as a whole because when the bolts are removed, the hydraulic engine is no longer held together.
FR 2 576 363 discloses a hydraulic radial piston engine in which the housing portion with the rotary cylinder and the further housing portion are connected as a structural unit to the rest of the transmission by bolts. This arrangement requires an additional housing plate between the transmission housing and the hydraulic engine, but this considerably increases the overall axial length.